I think often we forget how times have changed and how knew knowledge allows us to make more informed choices.
As a child I travelled loose in my carrycot in the back of my parents mini van, this was normal and I was given Phenergan when travelling to make me drowsy and to prevent travel sickness. We didn't fly but we did go on very long car journeys.
When my DC were small we had car seats but they were forward facing by 6 months and onto boosters very young, DC1 had travel sickness and we tried Phenergan which she hated and it did make her very sleepy, so we didn't use it on the plane but did after to help her get over jet lag, this was on advice but not prescribed.
Now I wouldn't dream of travelling in a car without a car seat, rear facing for as long as possible and I disagree with the legislation that says if you have 3 DC and can't fit in 3 car seats then the biggest can just sit in the middle with a normal seatbelt. I also wouldn't go near Phenergan or even suggest it in a joking manner to a relative or friend.
I would however agree that some DC need help with anxiety either because of a diagnosed SN or just because they may be a little scared and saying that we should just put up with it is a very strange and uncaring approach. I am sure there is a point between Phenergan/anesthesia and nothing.